Due to the increasing demand for quality of life, air conditioners are becoming widely used in people's daily lives. With growing concerns over environmental issues, air conditioners with high energy efficiency ratios (EER) are highly appreciated. A conventional way of improving the energy efficiency ratio is to use a combination of an inverter compressor and a fan. However, for a fixed-frequency air conditioner, the inverter compressor and the fan must be additionally provided, resulting in increased manufacturing costs.